Soil‐test biological activity with the flush of CO 2 : VIII. Soil type and management diversity

Soil Science Soc of Amer J

2022

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Soil erosion is a major constraint to agricultural sustainability. Land management that protects soil from water erosion can be assessed from the fraction of aggregates stable upon water immersion. Conservation management with minimal soil disturbance is known to enhance water‐stable aggregation, but how annual vs. perennial vegetative cover affects soil biological activity and aggregation from soils varying in texture remains relatively unexplored. This study assessed the effects of long‐term conventional‐till and no‐till cropland, grassland, and woodland on dry‐stable and water‐stable mean‐weight diameter (MWD) from 25 research stations across North Carolina. Soil clay concentration varied from 36 to 279 g kg–1 and sand concentration varied from 392 to 904 g kg–1 (5–95% distribution). Across locations, water‐stable MWD followed the order: conventional‐till cropland (0.64 mm) < no‐till cropland (0.87 mm) < woodland (1.12 mm) = grassland (1.15 mm). Soil stability index (i.e., water‐stable MWD/dry‐stable MWD) followed a similar order: conventional‐till cropland (0.59 mm mm–1) < no‐till cropland (0.76 mm mm–1) < grassland (0.92 mm mm–1) = woodland (0.96 mm mm–1). Although water‐stable MWD was positively associated with clay concentration (r = .50, p < .001, n = 310), soil‐test biological activity had the strongest association with water‐stable MWD (r = .80). Soil‐test biological activity reflected biological manipulation of surface‐concentrated organic matter, as mediated by conservation land uses. This study revealed the large impact of surface organic C and N resources on water‐stable aggregation through soil biological manipulations interacting across a textural gradient.

Section: Soil Properties Associated With Mean-weight Diametersupporting

confidence: 89%

Section: Methodsmentioning

confidence: 99%

Soil‐test biological activity associates with soil aggregation characteristics under different land uses in North Carolina

Soil Science Soc of Amer J

2022

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“…It was most strongly associated in this study with net N mineralization ( r = .96), cumulative C mineralization ( r = .96), soil microbial biomass C ( r = .88), particulate organic N ( r = .87), basal soil respiration ( r = .86), Mehlich 3 extractable Zn ( r = .77), total soil N ( r = .77), particulate organic C ( r = .76), sieved soil density ( r = −.76), and soil‐test K ( r = .74). With similarly strong associations between soil‐test biological activity and these organic C and N fractions in other studies (Franzluebbers & Stuedemann, 2008; Franzluebbers, Pershing, et al., 2018; 2021; Franzluebbers & Pershing, 2020), the case for its use as a soil health indicator is bolstered (Franzluebbers, 2016). Additionally, the strong negative association here with sieved soil density and moderate negative association with bulk density shown in Figure 2 give support for its use as a general soil health indicator that can simultaneously reveal several important functions of soil to store organic C and N, to cycle nutrients and water, and to create habitat for soil organisms.…”

Section: Resultsmentioning

confidence: 77%

Soil fertility characteristics in North Carolina pastures as affected by spatial separation and renovation with annual forages

Poore

2022

Agronomy Journal

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Spatial variation in soil properties is often considered significant across broad geographical regions due to soil formation factors. However, fine‐scale variations might also be significant. This study was conducted with the original intent of assessing how simple and complex mixtures of annual forages might be used to renovate perennial pastures. Private farmers in the Flatwoods, Piedmont, and Blue Ridge Major Land Resource Areas of North Carolina tested annual forages to renovate tall fescue pastures. Soil was sampled in multiple random locations in each field at depths of 0–6, 6–12, and 12–20 cm at the beginning and ending of a 3‐yr annual forage evaluation. Relative variation among five components (year of sampling [n = 2], physiographic region [n = 3], annual forage treatment [n = 2], soil depth [n = 3], and random variation from pseudoreplicates [n = 3 in 2015 and n = 5 in 2018]) was assessed for four soil physical, 10 soil biological, and 16 soil chemical properties. Soil chemical properties were mostly affected by physiographic region (47 ± 26% of total variation) and soil depth (33 ± 18%), soil biological properties were mostly affected by soil depth (63 ± 25%) and random pseudoreplication (14 ± 6%), and soil physical properties were equally affected by pseudoreplication (35 ± 21%), physiographic region (32 ± 18%), and soil depth (29 ± 22%). The type of annual forage had no discernible effect on soil properties, even the most biologically active. A diversity of spatial variations was important, suggesting that regional‐level ecological investigations require careful attention to an appropriate sampling design considering multiple factors.

“…Soil respiration can be measured from the same soil sample often collected to determine how much lime, phosphorus (P), or potassium (K) might be needed (i.e., from a surface sample that is dried and sieved). Soil‐test biological activity (STBA) is a standardized short‐term soil respiration protocol used in the Soil Ecology and Management Lab at North Carolina State University that is a simpler and less expensive indicator of the more complex biological process of mineralizable soil N, which along with mineralizable carbon (C) varies substantially depending on historical management (Franzluebbers et al., 2018; Franzluebbers & Pershing, 2020; Pehim‐Limbu & Franzluebbers, 2022). Across a diversity of fields in North Carolina, South Carolina, and Virginia, a strong linear association occurred between STBA and mineralizable soil N (Farmaha et al., 2022).…”

Section: Soil Health and Biological Activitymentioning

confidence: 99%

Adjusting the N fertilizer factor based on soil health as indicated by soil‐test biological activity

Agricultural & Env Letters

Shoemaker

Cline³

et al. 2022

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Agriculture faces a dilemma with nitrogen (N)—it is often the most necessary external input to optimize production, several generations of farmers became accustomed to its relatively inexpensive cost, and it contributes to widespread pollution due to numerous loss pathways to the environment. However, standard N fertilizer recommendations have not accounted well enough for a key source via mineralizable soil N. Soil‐test biological activity (STBA) is strongly associated with mineralizable soil N, both of which become surface‐enriched with conservation agricultural management using soil health principles. A series of field experiments assessed the contribution of mineralizable soil N to the N supply needed to optimize corn (Zea mays L.) grain and fall‐stockpiled tall fescue [Schedonorus arundinaceus (Schreb.) Dumort.] production. This essay synthesizes how STBA along with cost‐to‐value threshold can be used to modify the N fertilizer factor to optimize economic return and avoid environmental degradation.